Conventionally, there has been a device attached to a bicycle, for calculating information on the running of the bicycle, information on the movement of the cyclist, and the like to display. This type of device calculates predetermined information by receiving data from a sensor provided on the bicycle to display. The information to be displayed includes the force applied to the pedal by the cyclist (torque, and the like). Further, as a method for measuring this type of force, for example, Patent Literature 1 discloses a technique of measuring the strain on the crankshaft to detect the torque applied to the crank.
Furthermore, Patent Literature 2 discloses a technique of embedding a piezoelectric sensor in a crank to measure torque by using a voltage generated by the strain on the crank.
In addition, Patent Literature 1 describes that this technique can also be applied to a stationary bicycle-type health machine (also referred to as a bicycle ergometer or a fitness bike).
Thus, it is already known that in a human-powered machine including a crank, torque is measured by the detection of a strain applied to a crank and the momentum or the like is calculated.